Expression profiles of the organic acid metabolism-associated genes during rat liver regeneration

In this study, 55 of the organic acid metabolism-involved genes were primarily confirmed to be associated with liver regeneration (LR) by bioinformatics and gene expression profiling analysis. Number of the initially and totally expressed genes occurring in initiation phase of LR, G₀/G₁, cell proliferation, cell differentiation and liver tissue structure-function reconstruction were 21, 5, 33, 1 and 40, 20, 174, 44, respectively, illustrating that genes were initially expressed mainly in initiation stage, and worked in different phases. 151 times up-regulation and 114 times down-regulation as well as 14 types of expression patterns showed the diversification and complication of genes expression changes. It is inferred from the above gene expression changes and patterns that acetate biosynthesis enhanced at forepart, propionate biosynthesis at forepart, prophase and early metaphase, pyruvate biosynthesis at forepart, metaphase and anaphase, succinate biosynthesis at forepart and anaphase; malate biosynthesis in metaphase and N-acetylneuraminate biosynthesis at 36, 66 and 96 h. Whereas, carnitine biosynthsis attenuates at forepart and prophase, enhancement at middle metaphase; isocitrate in the forepart, quinolinate at forepart and early metaphase, creatine at early metaphase and fumarate at anaphase perform the restrained biosynthesis, respectively; catabolisms of propionate and pyruvate were depressed in metaphase.     

新基因BM390716、BI274487和AA963863与大鼠再生肝8种细胞的细胞外基质代谢

为了解新基因BM390716、BI274487、AA963863在细胞外基质代谢中的作用及其与大鼠肝再生的相关性,文章用Percoll密度梯度离心结合免疫磁珠分选分离大鼠再生肝的8种细胞,用Rat Genome 230 2.0芯片检测它们的基因表达变化,用Microsoft Excel、BLAST等软件分析基因的共表达关系、序列同源性及参与的代谢活动。结果表明,BM390716与pparα同源和共表达,BI274487与timp2同源和共表达,AA963863与csgalnact1同源和共表达。根据上述基因的同源性和共表达推测,新基因BM390716、BI274487和AA963863参与大鼠再生肝8种细胞的细胞外基质代谢。     

大鼠再生肝8种细胞的丝氨酸族氨基酸代谢相关基因的转录谱

为了解大鼠肝再生中8种肝脏细胞的丝氨酸族氨基酸代谢相关基因转录谱, 文章用Percoll密度梯度离心结合免疫磁珠分选分离大鼠的8种再生肝细胞, 用Rat Genome 230 2.0芯片等检测它们中丝氨酸族氨基酸代谢相关基因的表达变化, 用Cluster和Treeview等软件分析上述基因在肝再生中表达模式, 用生物信息学和系统生物学等方法分析上述细胞中丝氨酸族氨基酸代谢活动。结果表明, 在27个发生有意义表达变化的基因中, 肝细胞、胆管上皮细胞、卵圆细胞、肝星形细胞、窦内皮细胞、库普弗细胞、陷窝细胞、树突状细胞的基因数分别为13、16、11、14、13、11、12、14, 相应细胞的上调、下调和上/下调的基因数分别为7、6和0, 2、10和4, 2、8和1, 8、3和3, 6、5和2, 4、6和1, 2、10和0, 6、6和2。总的来看, 肝再生中各细胞的表达下调基因占优势, 但在肝再生启动阶段, 肝星形细胞和窦内皮细胞的表达上调基因占优势。上述丝氨酸族氨基酸代谢相关基因转录谱预示丝氨酸族氨基酸的合成主要在肝再生启动阶段的肝细胞、肝星形细胞、窦内皮细胞和库普弗细胞中增强, 它们的降解主要在肝再生进展阶段的肝细胞、胆管上皮细胞、陷窝细胞和树突状细胞中进行。     

Identification of the site of glucocorticoid action on neutral amino acid transport in superficial nephrons of rat kidney

Summary. Glucocorticoid hormones enhance the reabsorptive capacity of filtered amino acids in rat kidney, as it was shown in previous in vivo clearance experiments. In the present study, the site of glucocorticoid action on neutral amino acid transport in superficial nephrons of rat kidney was investigated using in vivo micropuncture technique. Adult female Wistar rats were treated with dexamethasone (DEX), and fractional excretion of L-glutamine (L-Gln) and L-leucine (L-Leu) were determined and related to inulin after microinfusion into different nephron segments. DEX reduced fractional excretion of both neutral amino acids as a sign of enhanced reabsorptive capacity. The site of main DEX action on L-Leu reabsorption has been localized in the proximal straight tubule. However, in the case of L-Gln, the inhibition of γ-glutamyltranspeptidase (γ-GT) by administration of acivicin indicated the importance of this brush border enzyme in reduced L-Gln excretion. DEX enhanced γ-GT activity by tubular acidification. It can be presumed a DEX-inducible transport system for neutral amino acids mainly localized in proximal straight tubules of rat kidney. Received July 8, 1999     

Plasma levels of amino acids in elderly long term care residents with oropharyngeal dysphagia: Comparison of hand-oral with tube-enteral-fed patients

Summary. Background: Dysphagia and eating difficulties are highly prevalent in long term care patients. Evaluation of their nutritional status is complicated by comorbidity, frailty and individual patterns of feeding. In previous studies we found vitamin deficiencies (folic acid B6 and B12) in orally fed elderly in early stages of oropharyngeal dysphagia despite satisfactory nutritional parameters (BMI, albumin and hemoglobin). The aim of this study is to evaluate the plasma amino acids levels in these hand-oral fed elderly patients with dysphagia. Methods: Plasma amino acids were measured in 15 orally fed elderly patients in early functional outcome swallowing scale (FOSS), stage 2, and compared with those of 15 matched nasogastric-tube-fed counterparts. Results: The plasma levels of all measured amino acids, ratio of essential to nonessential, levels of conditionally essential and the immune-enhancing amino acids were similar in both groups and within the normal range of our laboratory. The traditional nutritional parameters were also similar in both groups and within the normal range. Conclusions: Plasma levels of amino acids in elderly patients in early stage of FOSS are satisfactory, supporting the view that their protein intake is adequate. Further studies should concentrate on patients in advanced stages of FOSS.     

Effects of D-amino acids on lipoperoxidation in rat liver and kidney mitochondria

Summary. The effects of the amino acids D-ser, D-asp, and D-ala on lipoperoxidation under conditions of hypertension, alcoholism, and ammonemia in rat liver and kidney mitochondria were studied. Under normal conditions, D-alanine increased in 54% free radicals production in liver mitochondria (p < 0.05). The D-amino acids had no effect on kidney mitochondria. D-ser and D-ala increased lipoperoxidation in spontaneously hypertensive rats (SHR) as compared with their normotensive genetic control Wistar-Kyoto (WKY) rats (p < 0.05). During hypertension and in oxidative stress in the presence of calcium, only D-ala produced 46% and 29% free radicals in liver and kidney mitochondria (p < 0.05), respectively. During chronic alcoholism, D-ser increased lipoperoxidation in 80% in kidney mitochondria (p < 0.05), as compared to control. During ammonemia, D-ser produced 41% free radicals.     

Acetohydroxyacid synthase and its role in the biosynthetic pathway for branched-chain amino acids

Summary. The branched-chain amino acids are synthesized by plants, fungi and microorganisms, but not by animals. Therefore, the enzymes of this pathway are potential target sites for the development of antifungal agents, antimicrobials and herbicides. Most research has focused upon the first enzyme in this biosynthetic pathway, acetohydroxyacid synthase (AHAS) largely because it is the target site for many commercial herbicides. In this review we provide a brief overview of the important properties of each enzyme within the pathway and a detailed summary of the most recent AHAS research, against the perspective of work that has been carried out over the past 50 years.     

Bio-available amino acids and mineral nitrogen forms in soil of moderately mown and abandoned mountain meadows

Summary. The abandonment of traditional mowing methods of mountain meadows in the Czech Republic at the end of the last century has resulted in secondary re-colonization of these areas. Altered accumulation of plant biomass resulted in a deceleration of N turnover. A mountain meadow may be regarded as a N-limited ecosystem in which plant nutrition is dependent on direct uptake of soil amino acids. The composition and distribution of ammonium ions, nitrate ions and the 16 bio-available proteinaceuous amino acids were investigated in the top 7 cm of the Ah horizon of a Gleyic Luvisol in a long-term moderately mown meadow and an eleven year old, abandoned or uncut meadow. Ammonium N has a dominant role in both ecosystems. The moderately mown meadow showed accelerated N-turnover and higher net ammonization. The plant community showed a dependence on this form. Plant utilization of nitrates and amino acids appeared to be negligible. The uncut or abandoned meadow showed net ammonization from May (start of the experiment) through August, after which plant N-uptake consisted only of amino acids due to microbial immobilization. The release of bio-available nitrogen from spring until the beginning of summer in the Ah horizon was too low to explain total plant N-uptake. Glutamic acid, arginine and aspartic acids had the highest concentrations of any of the amino acids analyzed. Authors’ address: Pavel Formánek, Department of Geology and Pedology, Mendel University of Agriculture and Forestry, Zemedelska 3, 613 00 Brno, Czech Republic     

Phloem transport of amino acids in two Brassica napus L. genotypes and one B. carinata genotype in relation to their seed protein content

 In order to investigate the relationship between the amino acid concentration in the phloem sap of leaves and the protein content in seeds, two Brassica napus genotypes and one B. carinata genotype with low, medium and high seed protein contents were analyzed. Phloem sap was collected from the B. napus winter rapeseed breeding line DSV15 with 19% protein of dry weight in the seeds, the spring cultivar ‘Duplo’ with 25% protein in the seeds and from the B. carinata line BRA1151/90 with 39% protein in the seeds by using the aphid-stylet technique. The total amino acid contents measured in the phloem varied considerably among the three genotypes analysed, and correlated positively with their respective seed protein contents. The total amino acid-to-sucrose ratio was lowest in B. napus line DSV15 which had the lowest seed protein content and highest in the B. carinata line BRA1151/90 which had the highest seed protein content. The amino-N translocation in the phloem during the light period was about 2-fold higher in the B. carinata line BRA1151/90 than in the B. napus lines Dulpo and DSV15. Predominant amino acids in the phloem were glutamine and glutamate, followed by serine, aspartate, and threonine. The amino acid patterns in the leaves resembled those in the phloem, although their absolute concentrations were higher in the phloem than in the cytosol of mesophyll tissue. Furthermore, the concentration gradient of amino acids between the cytosol of mesophyll cells and the phloem was higher in the B. carinata line BRA1151/90 than in the B. napus lines Duplo and DSV15. These results lead to the conclusion that the phloem translocation of amino-N and the phloem loading process of amino acids are decisive factors for the protein content in the seeds of Brassica species. Received: 28 November 1999 / Accepted: 10 April 2000     

Excitatory amino acid stimulation of the survival of rat cerebellar granule cells in culture is associated with an increase in SMN, the spinal muscular atrophy disease gene product

Summary. Excitatory amino acids which promote the survival of cerebellar granule cells in culture, also promote the expression of the survival of motor neuron (SMN) protein. Immunolocalization studies using SMN monoclonal antibody showed that SMN is decreased in cultures grown in low K⁺ or chemically defined medium with respect to cultures grown in high K⁺ medium and that an increase of SMN can be induced by treatment of low K⁺ cultures with glutamate or N-methyl-D-aspartate. Received March 31, 1999     

Regulation of Growth Hormone (GH) secretion by different glutamate receptor subtypes in the rat

Summary. It has been firmly established that excitatory amino acids (EAAs), such as glutamate, are pivotal elements in the hypothalamic circuitry involved in the control of pituitary function. The actions of EAAs are mediated by different postsynaptic receptor subtypes, which include N-methyl D-aspartate (NMDA), kainate (KA), 2-amino-3-hydroxy-5 methyl-4-isoxazol propionic acid (AMPA) and metabotropic receptors. In this review, we summarize our experimental work on the role of EAA neurotransmission in the control of GH secretion in the rat. Detailed characterization of the effects of agonists and antagonists of glutamate receptors on GH release revealed that activation of NMDA, KA and AMPA receptors at different age-points resulted in clear-cut stimulation of GH secretion, although age- and sex-dependent differences were detected in the pattern of response to the different agonists. This stimulatory action was proven nitric oxide (NO)-dependent and not exerted at the pituitary level. In addition, evaluation of the role of hypothalamic GH-releasing hormone (GHRH) in the stimulatory action of NMDA by means of immunoneutralization of endogenous GHRH or destruction of GHRH producing neurons suggested the involvement of signals other than GHRH in this response. Further, evidence was obtained on the modulation of the EAA system by gonadal factors, and on the physiological relevance of EAA pathways in the regulation of pulsatile GH release. In conclusion, our data using the rat as animal model provide evidence for a pivotal role of glutamate pathways in the regulation of GH secretion throughout the life-span. Received May 5, 1999, Accepted July 28, 1999     

Blood amino acids concentration during insulin induced hypoglycemia in rats: the role of alanine and glutamine in glucose recovery

Summary. Our purpose was to determine the blood amino acid concentration during insulin induced hypoglycemia (IIH) and examine if the administration of alanine or glutamine could help glycemia recovery in fasted rats. IIH was obtained by an intraperitoneal injection of regular insulin (1.0 U/kg). The blood levels of the majority of amino acids, including alanine and glutamine were decreased (P < 0.05) during IIH and this change correlates well with the duration than the intensity of hypoglycemia. On the other hand, the oral and intraperitoneal administration of alanine (100 mg/kg) or glutamine (100 mg/kg) accelerates glucose recovery. This effect was partly at least consequence of the increased capacity of the livers from IIH group to produce glucose from alanine and glutamine. It was concluded that the blood amino acids availability during IIH, particularly alanine and glutamine, play a pivotal role in recovery from hypoglycemia.     

Action of the phosphonic analogue of tyrosine and of other tyrosine derivatives on rat liver tyrosine aminotransferase

Summary Tyrosine transamination has been investigatedin vitro with a preparation of rat liver tyrosine aminotransferase in the presence of several structural derivatives of the substrate, including the phosphonic analogue. The transamination by tyrosine aminotransferase (TAT) needs the presence in the substrate molecule of free amino and carboxylic groups, a three-carbon aliphatic chain, a para-phenolic hydroxylic function and al-configuration. Some tyrosine analogues can markedly disturb the Tyr-TAT association: the chief structural modifications are (i) the removal of the free amine function in a compound still possessing a para-hydroxylic and a carboxylic group, (ii) the change of the carboxylic function by another acidic group, especially a phosphonic one, (iii) a disubstitution in positions 3 and 5. In every situation, the presence of a parahydroxylic group is compulsory to observe an inhibitory effect.     

Influence of nitric oxide synthase activity on amino acid concentration in the quinolinate lesioned rat striatum: A microdialysis and histochemical study

Summary. The influence of nitric oxide synthase (NOS) activity on the KCl-evoked amino acid concentrations was investigated by in vivo microdialysis in the striatum in a rat model of excitotoxic lesion. Basal microdialysate levels of amino acids decreased during the quinolinic acid-induced neurodegeneration process, except for glutamine that increased initially and returned to control values 30 days after quinolinic acid exposure. KCl-evoked increase of extracellular amino acid concentration was reduced due to NOS activity in the striatum of both controls and lesioned animals, except for 120 days after quinolinic acid injection. These changes of amino acid concentrations in microdialysates correlated with the known biochemistry of the consecutive domineered cell types during the lesion process as revealed by histochemistry for NOS, NADPH-diaphorase, GFAP and isolectin B4. The present data provide direct evidence that NOS activity can modulate extracellular amino acid concentrations in the striatum not only under physiological conditions, but also during a pharmacologically induced lesion process and, thus, suggests that nitric oxide affects neurodegeneration via this pathway. Received October 20, 1999; Accepted February 25, 2000     

Relationships between the sedative and hypnotic effects of intracerebroventricular administration of L-serine and its metabolites, pyruvate and the derivative amino acids contents in the neonatal chicks under acute stressful conditions

Summary. Intracerebroventricular (i.c.v.) injection of L-serine was shown to have sedative and hypnotic effects on neonatal chicks under acute stressful conditions. To clarify the central mechanism of these effects of L-serine, two experiments were done. First, we focused on the glycogenic pathway in which L-serine is converted into pyruvate and finally glucose. I.c.v. administration of pyruvate (0.84 μmol) did not induce any behavioral and endocrinological changes, while L-serine and glucose triggered sedative and hypnotic effects. Secondly, the relationship between the sedation by L-serine and the metabolism into other amino acids which have sedative effects was investigated in the telencephalon and diencephalon. In both brain areas, a dose-dependent increase was seen in L-serine, although other amino acids were not changed. In the present study, it was concluded that the sedative action of L-serine was not due to the action of its metabolite pyruvate, or to the action of other amino acids. Authors’ address: M. Furuse, PhD, Laboratory of Advanced Animal and Marine Bioresources, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan     

Effects of endogenous glutamate on extracellular concentrations of taurine in striatum and nucleus accumbens of the awake rat: Involvement of NMDA and AMPA/kainate receptors

Summary. Using microdialysis, the effects of endogenous glutamate on extracellular concentrations of taurine in striatum and nucleus accumbens of the awake rat were investigated. The glutamate uptake inhibitor L-trans-pyrrolidine-2,4-dicarboxylic acid (PDC) was used to increase the extracellular concentration of glutamate. PDC (1, 2 and 4 mM) produced a dose-related increase of extracellular concentrations of glutamate and taurine in striatum and nucleus accumbens. Increases of extracellular taurine were significantly correlated with increases of extracellular glutamate, but not with PDC doses, which suggests that endogenous glutamate produced the observed increases of extracellular taurine in striatum and nucleus accumbens. The role of ionotropic glutamate receptors on the increases of taurine was also studied. In striatum, perfusion of the antagonists of NMDA and AMPA/kainate glutamate receptors attenuated the increases of extracellular taurine. AMPA/kainate, but not NMDA receptors, also reduced the increases of extracellular taurine in nucleus accumbens. These results suggest that glutamate-taurine interactions exist in striatum and nucleus accumbens of the awake rat. Received March 5, 1999/Accepted September 22, 1999     

Free and bound amino acids and proteins in developing grains of rice with enhanced lysine/proteins

 Free amino acids were determined in developing seed of a rice mutant with enhanced grain lysine. This phenotype frequently has enhanced protein. Some free amino acids of developing seed are inversely related to the level of total amino acids in proteins of the mature grain. Amino acids that were enhanced in protein, including aspartic acid, threonine, methionine and lysine, were notably lower in the free amino-acid pool. Our conclusion is that mutant-developing grains process aspartate amino acids more rapidly than the controls. Conversely, arginine, valine and glutamic acid/glutamine accumulate as free amino acids with mutant/control ratios of 1.39, 1.29 and 1.12, respectively. Glutamic acid/glutamine in proteins of mature seeds is lower in the mutant than the control. ³H-lysine incorporation showed enhanced isotope incorporation into at least four proteins. One mutant protein was less actively labelled than analogous controls. The ³Hlysine pattern indicates processing modifications in this useful rice mutant. Received: 14 October 1996/Accepted: 8 November 1996     

Preservation of amino acids during long term ischemia and subsequent reflow with supplementation of L-arginine,the nitric oxide precursor,in the rat heart

We investigated whether L-arginine, used in heart preservation to limit endothelial damage, may influence the pool of amino acids during long term ischemia and reflow. Isolated isovolumic rat hearts (n = 23) were submitted to 8 h of hypothermic ischemia after cardioplegic arrest with the Centre de Résonance Magnétique Biologique et Médicale (CRMBM) solution with or without L-arginine (Arg and No Arg groups respectively). Hearts were freeze-clamped after ischemia (n = 11) or submitted to 60 min of reflow (n = 12) and freeze-clamped. Eight hearts were perfused aerobically for 20 min and freeze-clamped (No ischemia group). Addition of L-arginine to the CRMBM solution limited aspartate depletion and decreased lysine level at the end of ischemia. After reflow, L-arginine supplementation increased the pool of glutamate and arginine and limited the depletion of serine, asparagine, glycine and taurine. We conclude that adding L-arginine to the CRMBM cardioplegic solution during long term ischemia preserved the amino acids pool.